Mechanical Engineering Commons™

1993

Aerospace engineering and engineering mechanics

Discipline

Articles 1 - 7 of 7

Full-Text Articles in Mechanical Engineering

Jan 1993

Solution Of Second Order Non-Linear Boundary Value Problems By The Boundary Element Method , Ravichandran V.

Retrospective Theses and Dissertations

In this work a procedure has been developed which makes it possible to use the boundary element method to solve non-linear partial differential equations of the second order in two variables. The problems solved are boundary value problems, and the non-linearity can be of any kind. A mathematical formulation is given which makes it unnecessary to have a knowledge of the fundamental solution for every type of non-linear equation. For second order partial differential equations, the use of Green's function for the Laplace equation as the fundamental solution has proved adequate to solve a wide variety of non-linear problems ...

A Numerical Investigation Of Laminar Airfoil Stall , Daniel Wayne Black Jan 1993

A Numerical Investigation Of Laminar Airfoil Stall , Daniel Wayne Black

Retrospective Theses and Dissertations

The details of an interacting boundary layer algorithm capable of calculating large scale laminar separation past airfoils at low speeds is given. Rationale behind various convergence acceleration methods is given. It is shown that linear based acceleration methods are limited to 50% savings in convergence rate. A nonlinear extrapolation method is proposed and tested on two simple model problems. Savings exceed the 50% limitation of the previous methods. Boundary layer results for laminar flow past symmetric airfoils at zero incidence are presented as a test of the methods. Leading edge marginal separation results at finite Reynolds numbers are presented. Richardson ...

Jan 1993

An Experimental Method For Structural Intensity And Source Location , Yong Zhang

Retrospective Theses and Dissertations

This study investigates the structural intensity and the force distribution function as tools to study vibrating plates. A laser Doppler vibrometer is used in measuring the plate normal velocity for the calculation of the structural intensity and the force distribution function. Several examples show the possibility of locating sources and studying the influence of ribs and damping material attached to the plate surface;There have been many studies on structural intensity. This thesis shows that the differences between two commonly used formulations are the assumptions that are used in deriving the formulas;The force distribution function is introduced in this ...

Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang Jan 1993

Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang

Retrospective Theses and Dissertations

A self-consistent mathematical formulation, using the Fourier transform method and a direct Gaussian numerical integration scheme, is developed and verified for analysis of both vibrational and acoustic responses of infinite submerged ribbed plates. Further steps developed from standard theories make structural intensity, acoustic intensity, and acoustic power calculations possible in the nearfield and farfield, and are demonstrated in this work;The direct numerical integration scheme adopted to obtain responses has proved to be straightforward and reliable. Although the double integration expression in some responses makes the technique infeasible, a practical way to overcome that difficulty is demonstrated using a standard ...

Application Of Displacement And Traction Boundary Integral Equations For Fracture Mechanics Analysis , Seungwon Youn

Retrospective Theses and Dissertations

A general formulation by dual boundary integral equations and a computational solution algorithm for the general mixed-mode crack in a linearly elastic, isotropic medium is presented. Traction boundary integral equations are collocated at the points on one crack surface while displacement boundary integral equations are collocated at the opposite points on the other surface to ensure a unique solution. The hypersingular and strongly singular integrals in the traction and displacement boundary integral equations are regularized before the numerical implementation. The singular integration elements on both crack surfaces are replaced by smooth curved auxiliary surfaces to avoid the direct integration over ...

Jan 1993

Computation Of The Integrated Aerodynamic And Propulsive Flowfields Of A Generic Hypersonic Space Plane , Ganesh Wadawadigi

Retrospective Theses and Dissertations

A new upwind, parabolized Navier-Stokes (PNS) code has been developed to compute two- and three-dimensional (3-D) chemically reacting, turbulent flows with hydrogen-air chemistry. The code is a modification of the 3-D upwind PNS (UPS) airflow code. The code solves the PNS equations using a finite-volume, upwind, TVD (Total Variation Diminishing) method based on Roe's approximate Riemann solver that has been modified to account for nonequilibrium effects. The fluid medium is assumed to be a chemically reacting mixture of thermally perfect (but calorically imperfect) gases in thermal equilibrium. Two turbulence models have been incorporated into the code including an algebraic ...

Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng Jan 1993

Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng

Retrospective Theses and Dissertations

The objective of this research is to investigate sound scattering by an object using a two-surface measurement technique that separates the incident field and the scattered field. The separation technique is developed in cartesian and cylindrical coordinates. The decomposition method in the cartesian coordinate system is based on the principle that any wave form can be decomposed into plane-wave components by using a two dimensional spatial Fourier transform. For the cylindrical coordinate system, a two plane separation technique is based on decomposing the sound field into cylindrical waves. Numerical simulations are performed and the effect of various parameters are investigated ...